FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
[See section 10, Rule 13]
POWER CONVERSION APPARATUS, MOTOR DRIVE DEVICE, AND
REFRIGERATION CYCLE APPLICATION DEVICE
MITSUBISHI ELECTRIC CORPORATION, A CORPORATION
ORGANISED AND EXISTING UNDER THE LAWS OF JAPAN, WHOSE
ADDRESS IS 7-3, MARUNOUCHI 2-CHOME, CHIYODA-KU, TOKYO
1008310, JAPAN
THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE
INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED
2
DESCRIPTION
Field
[0001] The present disclosure relates to a power
conversion apparatus that converts an alternating-current5
power into desired power, a motor drive device, and a
refrigeration cycle application device.
Background
[0002] Traditionally, there has been a power conversion10
apparatus that converts an alternating-current power
supplied from an alternating-current power supply into a
desired alternating-current power and supplies the
alternating-current power to a load such as an air
conditioner. For example, Patent Literature 1 discloses a15
technique in which a power conversion apparatus that is a
device for controlling an air conditioner rectifies an
alternating-current power supplied from an alternating-
current power supply with a diode stack that is a
rectifying unit, converts power smoothed by a smoothing20
capacitor into a desired alternating-current power with an
inverter including a plurality of switching elements, and
outputs the alternating-current power to a compressor motor
that is a load.
25
Citation List
Patent Literature
[0003] Patent Literature 1: Japanese Patent Application
Laid-open No. 7-71805
30
Summary of Invention
Problem to be solved by the Invention
[0004] However, according to the related art as
3
described above, a large current flows to a smoothing
capacitor. Therefore, there has been a problem in that
aged deterioration of the smoothing capacitor is
accelerated. In view of such a problem, a method for
preventing a ripple change of a capacitor voltage by5
increasing a capacity of the smoothing capacitor or a
method for using the smoothing capacitor having a large
deterioration tolerance by the ripple is considered.
However, cost of capacitor components increases, and a size
of a device increases.10
[0005] The present disclosure has been made in view of
the above, and an object of the present disclosure is to
obtain a power conversion apparatus that can prevent an
increase in size of the device while preventing
deterioration of a smoothing capacitor.15
Means to Solve the Problem
[0006] To solve the problem described above and achieve
the object, a power conversion apparatus according to the
present disclosure includes: a converter rectifying a first20
alternating-current voltage supplied from a three-phase
alternating-current power supply; a capacitor connected to
an output end of the converter, the capacitor smoothing a
first direct-current voltage obtained by rectification by
the converter into a second direct-current voltage25
containing a first ripple; an inverter connected across the
capacitor, the inverter converting the second direct-
current voltage into a second alternating-current voltage,
the second alternating-current voltage being dependent on a
desired frequency; and a detection unit detecting a30
physical quantity correlated with the second direct-current
voltage. The second alternating-current voltage is
controlled such that a second ripple correlated with the
4
first ripple is superimposed on an output voltage from the
inverter.
Effects of the Invention
[0007] A power conversion apparatus according to the5
present disclosure achieves an effect of preventing an
increase in size of the device, while preventing
deterioration of a smoothing capacitor.
Brief Description of Drawings10
[0008] FIG. 1 is a diagram illustrating a configuration
example of a power conversion apparatus according to a
first embodiment.
FIG. 2 is a diagram illustrating an example of
pulsation of a direct-current bus line voltage when a first15
alternating-current voltage supplied from an alternating-
current power supply is in a three-phase equilibrium state,
in the power conversion apparatus according to the first
embodiment.
FIG. 3 is a diagram illustrating an example of20
pulsation of the direct-current bus line voltage when the
first alternating-current voltage supplied from the
alternating-current power supply is in a three-phase non-
equilibrium state, in the power conversion apparatus
according to the first embodiment.25
FIG. 4 is a first block diagram illustrating a
configuration for generating a q-axis current command for
preventing the pulsation of the direct-current bus line
voltage included in a control unit of the power conversion
apparatus according to the first embodiment.30
FIG. 5 is a second block diagram illustrating the
configuration for generating the q-axis current command for
preventing the pulsation of the direct-current bus line
5
voltage included in the control unit of the power
conversion apparatus according to the first embodiment.
FIG. 6 is a first diagram illustrating a ratio of a
current amount of each control with respect to the q-axis
current command by the control unit of the power conversion5
apparatus according to the first embodiment.
FIG. 7 is a second diagram illustrating the ratio of
the current amount of each control with respect to the q-
axis current command by the control unit of the power
conversion apparatus according to the first embodiment.10
FIG. 8 is a flowchart illustrating an operation of the
control unit of the power conversion apparatus according to
the first embodiment.
FIG. 9 is a diagram illustrating an example of a
hardware configuration that implements the control unit15
included in the power conversion apparatus according to the
first embodiment.
FIG. 10 is a first diagram illustrating a
configuration example of a power conversion apparatus
according to a second embodiment.20
FIG. 11 is a second diagram illustrating the
configuration example of the power conversion apparatus
according to the second embodiment.
FIG. 12 is a diagram illustrating a configuration
example of a refrigeration cycle application device25
according to a third embodiment.
Description of Embodiments
[0009] Hereinafter, a power conversion apparatus, a
motor drive device, and a refrigeration cycle application30
device according to embodiments of the present disclosure
will be described in detail with reference to the drawings.
[0010] First Embodiment
6
FIG. 1 is a diagram illustrating a configuration
example of a power conversion apparatus 1 according to a
first embodiment. The power conversion apparatus 1 is
connected to an alternating-current power supply 110 and a
compressor 315. The power conversion apparatus 1 converts5
a first alternating-current voltage of a power supply
voltage Vs supplied from the alternating-current power
supply 110 that is a three-phase alternating-current power
supply into a second alternating-current voltage having a
desired amplitude and phase and supplies the second10
alternating-current voltage to the compressor 315. A
connection method of the alternating-current power supply
110 may be Y connection or Δ connection. The power
conversion apparatus 1 includes a voltage detection unit
501, a converter 150, a smoothing unit 200, a voltage15
detection unit 502, an inverter 310, current detection
units 313a and 313b, and a control unit 400. The converter
150 includes reactors 120 to 122 and a rectifying unit 130.
Note that the power conversion apparatus 1 and a motor 314
included in the compressor 315 constitute a motor drive20
device 2.
[0011] The voltage detection unit 501 detects a voltage
value of the first alternating-current voltage of the power
supply voltage Vs supplied from the alternating-current
power supply 110 and outputs the detected voltage value to25
the control unit 400. The voltage detection unit 501 is a
detection unit that detects a power state of the first
alternating-current voltage. Note that the voltage
detection unit 501 may detect a zero cross of the first
alternating-current voltage, as the power state of the30
first alternating-current voltage.
[0012] The converter 150 rectifies the first
alternating-current voltage of the power supply voltage Vs
7
supplied from the alternating-current power supply 110 that
is a three-phase alternating-current power supply. In the
converter 150, the reactors 120 to 122 are connected
between the alternating-current power supply 110 and the
rectifying unit 130. The rectifying unit 130 includes a5
rectifying circuit including rectifying elements 131 to 136
and rectifies and outputs the first alternating-current
voltage of the power supply voltage Vs supplied from the
alternating-current power supply 110. The rectifying unit
130 performs full-wave rectification.10
[0013] The smoothing unit 200 is connected to an output
end of the rectifying unit 130. The smoothing unit 200
includes a capacitor 210 as a smoothing element and smooths
a voltage rectified by the rectifying unit 130. The
capacitor 210 is, for example, an electrolytic capacitor, a15
film capacitor, or the like. The capacitor 210 is
connected to an output end of the converter 150,
specifically, the output end of the rectifying unit 130 and
has a capacity for smoothing the voltage rectified by the
rectifying unit 130. A voltage generated in the capacitor20
210 by smoothing does not have a full-wave rectification
waveform of the alternating-current power supply 110 and
has a waveform in which a voltage ripple according to a
frequency of the alternating-current power supply 110 is
superimposed on a direct-current component, and the voltage25
does not largely pulsate. In a case where the alternating-
current power supply 110 is a three-phase alternating-
current power supply, a frequency of the voltage ripple
mainly includes a six-fold component of a frequency of the
power supply voltage Vs. In a case where power input from30
the alternating-current power supply 110 and power output
from the inverter 310 do not change, an amplitude of the
voltage ripple is determined according to the capacity of
8
the capacitor 210. For example, the pulsation is performed
within a range in which a maximum value of the voltage
ripple generated in the capacitor 210 is less than twice of
a minimum value. In this way, the capacitor 210 is
connected to the output end of the converter 150, and5
smooths a first direct-current voltage rectified by the
converter 150 into a second direct-current voltage
including a first ripple.
[0014] The voltage detection unit 502 detects a direct-
current bus line voltage Vdc that is a voltage across the10
smoothing unit 200, that is, the capacitor 210 charged by
the current rectified by the rectifying unit 130 and
flowing from the rectifying unit 130 into the smoothing
unit 200 and outputs the detected voltage value to the
control unit 400. The voltage detection unit 502 is a15
detection unit that detects a physical quantity correlated
with the second direct-current voltage including the first
ripple, as the power state of the capacitor 210. In the
following description, the voltage detection unit 502 may
be referred to as a first detection unit, and the physical20
quantity detected by the voltage detection unit 502 may be
referred to as a first physical quantity.
[0015] The inverter 310 is connected across the
smoothing unit 200, that is, the capacitor 210. The
inverter 310 includes switching elements 311a to 311f and25
freewheeling diodes 312a to 312f. The inverter 310 turns
on/off the switching elements 311a to 311f under control of
the control unit 400, converts a voltage output from the
rectifying unit 130 and the smoothing unit 200 into the
second alternating-current voltage having the desired30
amplitude and phase, that is, generate the second
alternating-current voltage, and outputs the second
alternating-current voltage to the motor 314 of the
9
connected compressor 315. The inverter 310 converts the
second direct-current voltage including the first ripple
into the second alternating-current voltage dependent on a
desired frequency.
[0016] Each of the current detection units 313a and 313b5
detects a current value of one phase of three-phase
currents output from the inverter 310 and outputs the
detected current value to the control unit 400. Note that,
by acquiring current values of two phases among the current
values of the three phases output from the inverter 310,10
the control unit 400 can calculate the current value of the
remaining one-phase of the current output from the inverter
310. The current detection units 313a and 313b are
detection units that acquire a second physical quantity
including a third ripple correlated with a rotation speed15
generated by the motor 314. In the following description,
the current detection units 313a and 313b may be referred
to as a second detection unit.
[0017] The compressor 315 is a load including the motor
314 for compressor driving. The motor 314 rotates20
according to the amplitude and the phase of the second
alternating-current voltage supplied from the inverter 310
and performs a compression operation. For example, in a
case where the compressor 315 is a sealed compressor used
for an air conditioner or the like, a load torque of the25
compressor 315 can be often regarded as a constant torque
load. Regarding the motor 314, although a case where motor
winding is in Y connection is illustrated in FIG. 1, this
is an example, and the motor 314 is not limited to this.
The motor winding of the motor 314 may be Δ connection or30
may have a specification in which the Y connection and the
Δ connection can be switched.
[0018] Note that, in the power conversion apparatus 1,
10
arrangement of each configuration illustrated in FIG. 1 is
an example, and the arrangement of each configuration is
not limited to the example illustrated in FIG. 1. For
example, the power conversion apparatus 1 may include a
booster and may cause the rectifying unit 130 to have a5
function of a booster. In the following description, the
voltage detection units 501 and 502 and the current
detection units 313a and 313b may be collectively referred
to as a detection unit. Furthermore, the voltage values
detected by the voltage detection units 501 and 502 and the10
current values detected by the current detection units 313a
and 313b may be respectively referred to as a detection
value.
[0019] The control unit 400 acquires the voltage value
of the power supply voltage Vs of the first alternating-15
current voltage from the voltage detection unit 501,
acquires the voltage value of the direct-current bus line
voltage Vdc of the smoothing unit 200 from the voltage
detection unit 502, and acquires the current value of the
second alternating-current voltage having the desired20
amplitude and phase converted by the inverter 310, from the
current detection units 313a and 313b. The control unit
400 controls an operation of the inverter 310, specifically,
on/off of the switching elements 311a to 311f included in
the inverter 310, by using the detection value detected by25
each detection unit. Furthermore, the control unit 400
controls an operation of the motor 314, by using the
detection value detected by each detection unit. In the
present embodiment, the control unit 400 controls the
operation of the inverter 310 such that the second30
alternating-current voltage including pulsation according
to pulsation of the current flowing from the rectifying
unit 130 into the capacitor 210 of the smoothing unit 200
11
is output from the inverter 310 to the compressor 315 that
is a load. The pulsation according to the pulsation of the
current flowing into the capacitor 210 of the smoothing
unit 200 is, for example, pulsation that varies depending
on a frequency or the like of the pulsation of the current5
flowing into the capacitor 210 of the smoothing unit 200.
As a result, the control unit 400 reduces the current
flowing to the capacitor 210 of the smoothing unit 200.
Note that the control unit 400 does not need to use all of
the detection values acquired from each detection unit and10
may perform control by using some detection values. The
control unit 400 controls the second alternating-current
voltage such that a second ripple correlated with the first
ripple detected by the voltage detection unit 502 is
superimposed on an output voltage from the inverter 310.15
[0020] The control unit 400 performs control such that
any one of a speed, a voltage, and a current of the motor
314 is in a desired state. Here, in a case where the motor
314 is used to drive the compressor 315 and the compressor
315 is a sealed compressor, it is difficult to attach a20
position sensor that detects a rotor position to the motor
314 in terms of structure and cost. Therefore, the control
unit 400 controls the motor 314 without the position sensor.
As a method for controlling the motor 314 without the
position sensor, there are two types of methods including25
primary magnetic flux constant control and sensorless
vector control. In the present embodiment, as an example,
the sensorless vector control will be described. Note that
the control method to be described below can be applied to
the primary magnetic flux constant control with a minor30
change. In the present embodiment, as will be described
later, the control unit 400 controls the operations of the
inverter 310 and the motor 314, by using dq rotation
12
coordinates that rotate in synchronization with the rotor
position of the motor 314.
[0021] Control for reducing the current flowing to the
capacitor 210 of the smoothing unit 200 by the control unit
400 will be described below. As illustrated in FIG. 1, in5
the power conversion apparatus 1, an input current from the
rectifying unit 130 to the capacitor 210 of the smoothing
unit 200 is referred to as an input current I1, an output
current from the capacitor 210 of the smoothing unit 200 to
the inverter 310 is referred to as an output current I2,10
and a charge/discharge current of the capacitor 210 of the
smoothing unit 200 is referred to as a charge/discharge
current I3. In this case, a relationship of the input
current I1=the output current I2+the charge/discharge
current I3 is satisfied. Flowing the charge/discharge15
current I3 in the capacitor 210 means that the capacitor
210 is charged/discharged, and a voltage across the
capacitor 210, that is, the direct-current bus line voltage
Vdc is pulsated by charging/discharging the capacitor 210.
Therefore, the control unit 400 reduces the20
charge/discharge current I3 of the capacitor 210, by
performing control for preventing the pulsation of the
direct-current bus line voltage Vdc. The control unit 400
can reduce the charge/discharge current I3 of the capacitor
210, by adding a current corresponding to the pulsation of25
the direct-current bus line voltage Vdc to the output
current I2.
[0022] The pulsation of the direct-current bus line
voltage Vdc is affected by the alternating-current power
supply 110 that is the three-phase alternating-current30
power supply, and includes two types of frequency
components that are roughly divided. Specifically, the two
types include a frequency component that is six times as
13
large as the power supply frequency of the alternating-
current power supply 110 generated by overlap of the phases
of the three-phase alternating-current and a frequency
component that is twice as large as the power supply
frequency of the alternating-current power supply 1105
generated by non-equilibrium of the three-phase
alternating-current. FIG. 2 is a diagram illustrating an
example of the pulsation of the direct-current bus line
voltage Vdc when the first alternating-current voltage
supplied from the alternating-current power supply 110 is10
in a three-phase equilibrium state, in the power conversion
apparatus 1 according to the first embodiment. FIG. 3 is a
diagram illustrating an example of the pulsation of the
direct-current bus line voltage Vdc when the first
alternating-current voltage supplied from the alternating-15
current power supply 110 is in a three-phase non-
equilibrium state, in the power conversion apparatus 1
according to the first embodiment. Here, a power supply
frequency of the alternating-current power supply 110 that
is the three-phase alternating-current power supply, that20
is, a fundamental frequency of the first alternating-
current voltage, is set as f.
[0023] As illustrated in FIG. 2, in a case where the
first alternating-current voltage is in the three-phase
equilibrium state, the pulsation of the direct-current bus25
line voltage Vdc is 6f cycles. As illustrated in FIG. 3,
in a case where the first alternating-current voltage is in
the three-phase non-equilibrium state, the pulsation of the
direct-current bus line voltage Vdc is 2f cycles. In a
case where the power supply frequency of the alternating-30
current power supply 110 that is the three-phase
alternating-current power supply, that is, the fundamental
frequency of the first alternating-current voltage, is 50
14
Hz, 6f=300 Hz, and 2f=100 Hz. The frequency of the first
ripple is a frequency that is twice or six times as large
as the power supply frequency of the alternating-current
power supply 110 that is the three-phase alternating-
current power supply, that is, the fundamental frequency of5
the first alternating-current voltage. Note that, in FIGS.
2 and 3, the fundamental frequency f is written as a power
supply 1f, the pulsation frequency of the direct-current
bus line voltage Vdc when the first alternating-current
voltage is in the three-phase equilibrium state is written10
as a power supply 6f, and the pulsation frequency of the
direct-current bus line voltage Vdc when the first
alternating-current voltage is in the three-phase non-
equilibrium state is written as a power supply 2f. In the
actual power conversion apparatus 1, pulsations in various15
frequency bands are generated according to effects of
wiring of the alternating-current power supply 110 and an
operation state of the compressor 315 that is the load.
However, the pulsation is omitted here.
[0024] If a pulsation state of the direct-current bus20
line voltage Vdc can be correctly acquired, the control
unit 400 can perform control for preventing the pulsation
of the direct-current bus line voltage Vdc, by controlling
the operations of the inverter 310, the motor 314, or the
like. In the present embodiment, since the voltage25
detection unit 502 directly detects the voltage value of
the direct-current bus line voltage Vdc, the control unit
400 can correctly acquire the pulsation state of the
direct-current bus line voltage Vdc, by acquiring the
detection value from the voltage detection unit 502. Note30
that the method for acquiring the pulsation state of the
direct-current bus line voltage Vdc by the control unit 400
is not limited to this. For example, it is possible to
15
estimate the pulsation state of the direct-current bus line
voltage Vdc from a current flowing to a bus line of the
power conversion apparatus 1, and it is possible to
estimate the pulsation state of the direct-current bus line
voltage Vdc from a current flowing to the capacitor 210.5
Therefore, the control unit 400 may acquire a detection
value from a detection unit that detects the current
flowing to the bus line of the power conversion apparatus 1,
a detection unit that detects the current flowing to the
capacitor 210, or the like (not illustrated in FIG. 1), and10
estimate the pulsation state of the direct-current bus line
voltage Vdc. For example, the control unit 400 can
calculate the pulsation of the direct-current bus line
voltage Vdc, by using a general capacitor voltage-current
method, that is, "I=C×dV/dt"→"dV/dt=I/C".15
[0025] In this way, the control unit 400 can extract a
frequency component of the pulsation of the direct-current
bus line voltage Vdc, by acquiring a physical quantity
correlated with the pulsation of the direct-current bus
line voltage Vdc, such as an instantaneous value of the20
direct-current bus line voltage Vdc or an instantaneous
value of the current flowing to the capacitor 210. The
physical quantity correlated with the direct-current bus
line voltage Vdc is the instantaneous value of the direct-
current bus line voltage Vdc that is the second direct-25
current voltage including the first ripple or the
instantaneous value of the current flowing to the capacitor
210.
[0026] As described above, the control unit 400 detects
the pulsation of the direct-current bus line voltage Vdc30
corresponding to the charge/discharge current I3 that is
the current flowing to the capacitor 210 and controls an
inverter output to prevent the pulsation, so as to
16
indirectly reduce the current flowing to the capacitor 210,
that is, the charge/discharge current I3. Here,
information necessary for the control by the control unit
400 includes the detection value of the direct-current bus
line voltage Vdc and the frequency component of the5
pulsation of the direct-current bus line voltage Vdc.
[0027] FIG. 4 is a first block diagram illustrating a
configuration for generating a q-axis current command for
preventing the pulsation of the direct-current bus line
voltage Vdc included in the control unit 400 of the power10
conversion apparatus 1 according to the first embodiment.
The configuration illustrated in FIG. 4 is formed by a
feedback loop in which a value of the q-axis current
command is zero, in order to set the pulsation of the
direct-current bus line voltage Vdc to zero. Although the15
direct-current bus line voltage Vdc can be obtained
according to the detection value of the voltage detection
unit 502, a value estimated from a detection value of
another detection unit may be used as described above. In
the following description, the q-axis current command with20
the value of zero may be abbreviated and written as a
command value 0.
[0028] A secondary low-pass filter 401 transmits a
direct-current component of the direct-current bus line
voltage Vdc. A subtraction unit 402 removes the direct-25
current component from the direct-current bus line voltage
Vdc, by subtracting the direct-current component of the
direct-current bus line voltage Vdc that has passed through
the secondary low-pass filter 401 from the direct-current
bus line voltage Vdc. That is, a filter 403 is a kind of30
high-pass filter that removes the direct-current component
from the direct-current bus line voltage Vdc. Note that,
since an object of the filter 403 is to increase accuracy
17
of extraction of a pulsation component to be described
later, the filter 403 may be omitted. A subtraction unit
404 calculates a difference between the command value 0 and
the direct-current bus line voltage Vdc from which the
direct-current component has been removed.5
[0029] A pulsation component extraction unit 405
converts a specific frequency component, specifically, a
cos2f component, from the difference between the command
value 0 and the direct-current bus line voltage Vdc from
which the direct-current component has been removed into a10
direct current and extracts the direct current. The
reference character 2f indicates a frequency that is twice
as large as the power supply frequency of the alternating-
current power supply 110, that is, the fundamental
frequency of the first alternating-current voltage. A15
pulsation component extraction unit 407 converts a specific
frequency component, specifically, a sin2f component, from
the difference between the command value 0 and the direct-
current bus line voltage Vdc from which the direct-current
component has been removed into a direct current and20
extracts the direct current. The pulsation component
extraction units 405 and 407 prevent generation of beats,
sideband waves, or the like and make a waveform be less
likely to be distorted, by extracting and reducing only the
pulsation of the specific frequency component. The control25
unit 400 performs simple Fourier transform by integrating a
trigonometric function cos2f having a frequency same as the
specific frequency component to be extracted by the
pulsation component extraction unit 405 and integrating a
trigonometric function sin2f having a frequency same as the30
specific frequency component to be extracted by the
pulsation component extraction unit 407.
[0030] An integration control unit 406 performs
18
integration control such that the frequency component
extracted by the pulsation component extraction unit 405
becomes zero and calculates a necessary current amount. An
integration control unit 408 performs integration control
such that the frequency component extracted by the5
pulsation component extraction unit 407 becomes zero and
calculates a necessary current amount. Note that the
integration control units 406 and 408 may perform
calculation in combination with proportional control,
differential control, or the like, in addition to the10
integration control.
[0031] An alternating-current restoration processing
unit 409 uses the calculation results of the integration
control units 406 and 408 as inputs, and restores the
calculation results into a single alternating-current15
signal. The alternating-current restoration processing
unit 409 outputs the restored alternating-current signal as
the q-axis current command. As a result, the control unit
400 can pulsate a q-axis current at the same frequency as
the direct-current bus line voltage Vdc and pulsate the20
output voltage of the inverter 310.
[0032] Note that, in the example in FIG. 4, in order to
prevent the pulsation of the frequency component that is
twice as large as the fundamental frequency of the first
alternating-current voltage, the control unit 400 extracts25
the frequency component that is twice as large as the
fundamental frequency of the first alternating-current
voltage by the pulsation component extraction units 405 and
407. However, in a case where it is desired to prevent the
pulsation of the frequency component that is six times as30
large as the fundamental frequency of the first
alternating-current voltage as described above, it is
sufficient to extract the frequency component that is six
19
times as large as the fundamental frequency of the first
alternating-current voltage by the pulsation component
extraction units 405 and 407. Furthermore, in a case where
it is desired to prevent the pulsations of the plurality of
frequency components, for example, in a case where it is5
desired to prevent the pulsations of the frequency
components that are twice and six times as large as the
fundamental frequency of the first alternating-current
voltage, the control unit 400 can provide the pulsation
component extraction units and the integration control10
units, as many as the number of frequencies, in parallel,
and extract the frequency components that are twice and six
time as large as the fundamental frequency of the first
alternating-current voltage.
[0033] FIG. 5 is a second block diagram illustrating the15
configuration for generating the q-axis current command for
preventing the pulsation of the direct-current bus line
voltage Vdc included in the control unit 400 of the power
conversion apparatus 1 according to the first embodiment.
In the configuration illustrated in FIG. 5, pulsation20
component extraction units 410 and 412 and integration
control units 411 and 413 are added to the configuration
illustrated in FIG. 4.
[0034] The pulsation component extraction unit 410
converts a specific frequency component, specifically, a25
cos6f component, from the difference between the command
value 0 and the direct-current bus line voltage Vdc from
which the direct-current component has been removed into a
direct current and extracts the direct current. The
reference character 6f indicates a frequency that is six30
times as large as the power supply frequency of the
alternating-current power supply 110, that is, the
fundamental frequency of the first alternating-current
20
voltage. The pulsation component extraction unit 412
converts a specific frequency component, specifically, a
sin6f component, from the difference between the command
value 0 and the direct-current bus line voltage Vdc from
which the direct-current component has been removed into a5
direct current and extracts the direct current. Effects
obtained by the pulsation component extraction units 410
and 412 are as described about the pulsation component
extraction units 405 and 407 described above.
[0035] The integration control unit 411 performs10
integration control such that the frequency component
extracted by the pulsation component extraction unit 410
becomes zero and calculates a necessary current amount.
The integration control unit 413 performs integration
control such that the frequency component extracted by the15
pulsation component extraction unit 412 becomes zero and
calculates a necessary current amount. Note that the
integration control units 411 and 413 may perform
calculation in combination with proportional control,
differential control, or the like, in addition to the20
integration control.
[0036] The alternating-current restoration processing
unit 409 uses the calculation results of the integration
control units 406, 408, 411, and 413 as inputs, and
restores the calculation results into a single alternating-25
current signal. The alternating-current restoration
processing unit 409 outputs the restored alternating-
current signal as the q-axis current command. As a result,
the control unit 400 can pulsate a q-axis current at the
same frequency as the direct-current bus line voltage Vdc30
and pulsate the output voltage of the inverter 310.
[0037] The control unit 400 adds the q-axis current
command necessary for preventing the pulsation of the
21
direct-current bus line voltage Vdc to an existing q-axis
current command. Here, the existing q-axis current command
will be described. A magnetic flux direction of a motor
magnet is defined as a d-axis, and a direction advanced by
90 degrees in an electrical angle phase from the d-axis,5
that is, a direction orthogonal to the d-axis, is defined
as a q-axis. It is a known technique that, by flowing a
current Iq to a motor coil in the q-axis direction, a
torque is generated in the motor 314 and generates a
rotational force. In general, the control unit 400 of the10
power conversion apparatus 1 connected to the motor 314
includes a speed control unit (not illustrated) used to
control the motor 314 to have a desired rotation speed.
Since it is sufficient that a configuration of the speed
control unit be a general configuration, detailed15
description is omitted. When an output of the speed
control unit is denoted by iqpi, the existing q-axis current
command iq* is represented by Expression (1).
[0038] iq*=iqpi (1)
[0039] Next, when an amplitude component of the20
pulsation of the direct-current bus line voltage Vdc is
denoted by Iqvdc, an angular speed of a frequency that is
twice as large as the fundamental frequency of the first
alternating-current voltage supplied from the alternating-
current power supply 110 is denoted by 2ωin, and a phase of25
the pulsation of the direct-current bus line voltage Vdc is
denoted by δ, the q-axis current command necessary for
preventing the pulsation of the direct-current bus line
voltage Vdc is represented by Expression (2).
[0040] Iqvdcsin(2ωin+δ) (2)30
[0041] Therefore, when the q-axis current command
necessary for preventing the pulsation of the direct-
current bus line voltage Vdc is added to the existing q-
22
axis current command iq*, this is represented by Expression
(3).
[0042] iq*=iqpi+Iqvdcsin(2ωin+δ) (3)
[0043] In order to prevent the pulsation of the direct-
current bus line voltage Vdc, the control unit 4005
generates the q-axis current command iq* represented by
Expression (3) and controls the operations of the inverter
310, the motor 314, or the like. Note that, in a case
where a frequency that is six times as large as the
fundamental frequency of the first alternating-current10
voltage is desired to be targeted, it is sufficient that
the control unit 400 set 2ωin as 6ωin in Expressions (2) and
(3). Furthermore, in a case where a plurality of
frequencies is targeted when the pulsation of the direct-
current bus line voltage Vdc is prevented, specifically, a15
frequency that is twice or six times as large as the
fundamental frequency of the first alternating-current
voltage is targeted, the control unit 400 may generate a q-
axis current command iq* denoted by Expression (4) and
control the operations of the inverter 310, the motor 314,20
or the like.
[0044] iq*=iqpi+Iqvdcsin(2ωin+δ)+Iqvdcsin(6ωin+δ) (4)
[0045] Furthermore, the control unit 400 may further add
the q-axis current command used for vibration preventing
control of the motor 314 to the q-axis current command iq*25
represented by Expressions (3) or (4). A load pulsation
generated by the rotation of the motor 314 of the
compressor 315 can be prevented by a q-axis current command
output from a pulsation compensation unit as described in
Japanese Patent No. 6537725, for example. Therefore, it is30
sufficient that the control unit 400 include such a
pulsation compensation unit. When an amplitude component
of the load pulsation of the compressor 315 is denoted by
23
Iqavs, an angular speed of a mechanical angular rotation
frequency of the compressor 315 is denoted by ωm, and a
phase of the load pulsation of the compressor 315 is
denoted by ε, the q-axis current command output from the
pulsation compensation unit is represented by Expression5
(5).
[0046] Iqavssin(ωm+ε) (5)
[0047] The control unit 400 controls the second
alternating-current voltage such that a fourth ripple
correlated with the third ripple is superimposed on the10
output voltage from the inverter 310. Therefore, when the
q-axis current command for the vibration preventing control
is added to the q-axis current command in Expressions (3)
and (4), the q-axis current commands are respectively
represented by Expressions (6) and (7).15
[0048] iq*=iqpi+Iqvdcsin(2ωin+δ)+Iqavssin(ωm+ε) (6)
[0049]
iq*=iqpi+Iqvdcsin(2ωin+δ)+Iqvdcsin(6ωin+δ)+Iqavssin(ωm+ε)
(7)
[0050] The control unit 400, in order to prevent the20
pulsation of the direct-current bus line voltage Vdc and
further perform the vibration preventing control, generates
the q-axis current command iq* represented by Expressions
(6) or (7) and controls the operations of the inverter 310,
the motor 314, or the like. Here, since a current amount25
to be flown as a q-axis current is actually limited, that
is, a maximum current amount is set, a case is considered
where it is not possible to flow the current amount as in
the q-axis current commands iq* in Expressions (3), (4),
(6), and (7). Therefore, the control unit 400 sets a limit30
value to the q-axis current command for each control. A
method for setting the limit value includes, for example, a
method for determining a priority and allocating the q-axis
24
current each time, a method for distributing the q-axis
current at a ratio determined from the beginning, or the
like. For the former case, for example, the priority is
determined as iqpi>Iqvdc>Iqavs. For the latter case, for
example, a limit value of a usable q-axis current is5
divided as iqpi:Iqvdc:Iqavs=4:3:3.
[0051] Furthermore, the control unit 400 may distribute
a remaining current amount obtained by subtracting the q-
axis current command iqpi from the maximum current amount to
the q-axis current command Iqvdc used to prevent the10
pulsation of the direct-current bus line voltage Vdc and
the q-axis current command Iqavs from the pulsation
compensation unit, instead of limiting the q-axis current
command iqpi from the speed control unit. FIG. 6 is a first
diagram illustrating a ratio of the current amount of each15
control with respect to the q-axis current command iq* by
the control unit 400 of the power conversion apparatus 1
according to the first embodiment. FIG. 7 is a second
diagram illustrating the ratio of the current amount of
each control with respect to the q-axis current command iq*20
by the control unit 400 of the power conversion apparatus 1
according to the first embodiment. Note that FIGS. 6 and 7
are for Expression (6), and Iqvdc2 represents Iqvdcsin(2ωin+δ).
As illustrated in FIG. 6, the control unit 400 may allocate
the q-axis current command iqpi and the q-axis current25
command Iqvdc2 as they are to the maximum current amount and
may allocate the remaining current amount to the q-axis
current command Iqavs. Furthermore, as illustrated in FIG.
7, the control unit 400 may allocate the q-axis current
command iqpi to the maximum current amount as it is and may30
equally divide the remaining current amount into two and
allocate the remaining amount to the q-axis current command
Iqvdc2 and the q-axis current command Iqavs. In a case where
25
Expression (7) is used in the example in FIG. 7, the
control unit 400 may allocate the q-axis current command
iqpi to the maximum current amount as it is and may equally
divide the remaining current amount into three and allocate
the remaining current amount to the q-axis current command5
Iqvdc2, the q-axis current command Iqvdc6, and the q-axis
current command Iqavs. Note that it is assumed that Iqvdc6
represents Iqvdcsin(6ωin+δ).
[0052] When the current of the q-axis current command
iqpi that is the output from the speed control unit is10
limited, since it is not possible for the control unit 400
to keep desired rotation of the motor 314, the q-axis
current command iqpi is basically prioritized. However, the
q-axis current command iqpi may be limited depending on an
application in which it is desired to continue the15
operation even if the rotation speed of the motor 314 is
lowered. Furthermore, in FIGS. 6 and 7, the control unit
400 may freely set a ratio to each control according to an
object. For example, when vibration is concerned at a low
speed, the control unit 400 may allocate more currents to20
the q-axis current command Iqavs.
[0053] In this way, the control unit 400 can reduce the
pulsation of the direct-current bus line voltage Vdc, by
superimposing the pulsation including the frequency
component same as the pulsation of the direct-current bus25
line voltage Vdc generated by the alternating-current power
supply 110 that is the three-phase alternating-current
power supply on the inverter output. The control unit 400
uses the frequency that is six times or twice as large as,
or both of the frequency six times as large as and the30
frequency that is twice as large as the power supply
frequency of the alternating-current power supply 110 that
is the three-phase alternating-current power supply, that
26
is, the fundamental frequency of the first alternating-
current voltage, as the frequency component. In a case
where both of the frequencies that are six times and twice
as large as the power supply frequency of the alternating-
current power supply 110 that is the three-phase5
alternating-current power supply, that is, the fundamental
frequency of the first alternating-current voltage, are
used, the control unit 400 may increase one frequency
component and decrease another frequency component. For
example, as illustrated in FIGS. 2 and 3, if the first10
alternating-current voltage supplied from the alternating-
current power supply 110 is in the three-phase equilibrium
state, the direct-current bus line voltage Vdc pulsates at
the frequency that is six times as large as the fundamental
frequency of the first alternating-current voltage, and if15
the first alternating-current voltage supplied from the
alternating-current power supply 110 is in the three-phase
non-equilibrium state, the direct-current bus line voltage
Vdc pulsates at the frequency that is twice as large as the
fundamental frequency of the first alternating-current20
voltage. Therefore, the control unit 400 may change a
ratio of the frequency of the pulsation to be superimposed
on the inverter output, according to the equilibrium state
of the first alternating-current voltage supplied from the
alternating-current power supply 110. In this case, the25
frequency of the first ripple is a sum of the frequency
components that are twice and six times as large as the
power supply frequency of the alternating-current power
supply 110 that is the three-phase alternating-current
power supply, that is, the fundamental frequency of the30
first alternating-current voltage.
[0054] Note that the control unit 400 can determine
whether or not the first alternating-current voltage
27
supplied from the alternating-current power supply 110 is
balanced according to the detection value from the voltage
detection unit 501. Furthermore, the control unit 400 may
estimate whether or not the first alternating-current
voltage supplied from the alternating-current power supply5
110 is balanced from the output of the pulsation component
extraction unit illustrated in FIG. 5. In this way, the
control unit 400 changes a ratio of the frequency component
that is twice as large as the fundamental frequency of the
first alternating-current voltage and the frequency10
component that is six times as large as the fundamental
frequency of the first alternating-current voltage, in the
sum, according to the equilibrium state of the voltages of
the respective phases of the first alternating-current
voltage.15
[0055] Furthermore, the control unit 400 periodically
calculates the fundamental frequency of the first
alternating-current voltage that is the power supply
frequency of the alternating-current power supply 110 that
is the three-phase alternating-current power supply, by20
using the detection value of the voltage detection unit 501.
The power supply frequency of the alternating-current power
supply 110 may slightly vary in one day. Therefore, the
control unit 400 can improve accuracy of the control
described above, by periodically calculating the25
fundamental frequency of the first alternating-current
voltage that is the power supply frequency of the
alternating-current power supply 110.
[0056] The operation of the control unit 400 will be
described with reference to a flowchart. FIG. 8 is a30
flowchart illustrating the operation of the control unit
400 of the power conversion apparatus 1 according to the
first embodiment. In the power conversion apparatus 1, the
28
control unit 400 acquires the physical quantity correlated
with the direct-current bus line voltage Vdc (step S1).
The control unit 400 specifies the first ripple included in
the direct-current bus line voltage Vdc (step S2). The
control unit 400 generates the q-axis current command such5
that the second ripple correlated with the first ripple is
superimposed on the output voltage from the inverter 310
(step S3).
[0057] A hardware configuration of the control unit 400
included in the power conversion apparatus 1 will be10
described below. FIG. 9 is a diagram illustrating an
example of a hardware configuration that implements the
control unit 400 included in the power conversion apparatus
1 according to the first embodiment. The control unit 400
is implemented by a processor 91 and a memory 92.15
[0058] The processor 91 is, for example, a central
processing unit (CPU) (also referred to as a central
processing unit, a processing device, an arithmetic device,
a microprocessor, a microcomputer, a processor, or a
digital signal processor (DSP)) or a system large scale20
integration (LSI). The memory 92 can be a nonvolatile or
volatile semiconductor memory, such as a random access
memory (RAM), a read only memory (ROM), a flash memory, an
erasable programmable read only memory (EPROM), or an
electrically erasable programmable read only memory25
(EEPROM) (registered trademark). Furthermore, the memory
92 is not limited to these and may be a magnetic disk, an
optical disk, a compact disk, a mini disk, or a digital
versatile disc (DVD).
[0059] As described above, according to the present30
embodiment, in the power conversion apparatus 1, the
control unit 400 can reduce the pulsation of the direct-
current bus line voltage Vdc, by superimposing the
29
pulsation including the frequency component same as the
pulsation of the direct-current bus line voltage Vdc
generated by the alternating-current power supply 110 that
is the three-phase alternating-current power supply on the
inverter output. Furthermore, the power conversion5
apparatus 1 can prevent an increase in size of the device
while preventing deterioration of the smoothing capacitor
210.
[0060] Second Embodiment
In a second embodiment, a case where a converter10
includes a booster circuit will be described.
[0061] FIG. 10 is a diagram illustrating a configuration
example of a power conversion apparatus 1a according to the
second embodiment. The power conversion apparatus 1a is
obtained by replacing the converter 150 and the control15
unit 400 in the power conversion apparatus 1 according to
the first embodiment illustrated in FIG. 1 with a converter
150a and a control unit 400a. The converter 150a includes
the reactors 120 to 122, the rectifying unit 130, and a
booster 140. The booster 140 includes a reactor 141, a20
switching element 142, and a rectifying element 143 and
constitutes a booster circuit. The booster 140 boosts a
voltage rectified by the rectifying unit 130, by
controlling on/off of the switching element 142 by the
control unit 400a. Since it is sufficient that a boosting25
operation of the booster 140 be a general operation,
detailed description is omitted. The control unit 400a has
the function of the control unit 400 and a function for
controlling on/off of the switching element 142 of the
booster 140. That is, the control unit 400a controls an30
operation of the converter 150a including the booster 140.
Note that the power conversion apparatus 1a and the motor
314 included in the compressor 315 constitute a motor drive
30
device 2a.
[0062] For example, since a current for weak magnetic
flux control or the like is not necessary for the rotation
of the motor 314 by installing the booster circuit and
increasing the direct-current bus line voltage Vdc, the5
power conversion apparatus 1a can increase a current amount
that can be used for the q-axis current as compared with a
case where the converter 150 is a passive circuit as in the
first embodiment. As compared with the power conversion
apparatus 1 according to the first embodiment, the power10
conversion apparatus 1a can increase a current that can be
allocated to the q-axis current command Iqvdc under the same
load condition and at a rotational speed, or the like and
can enhance an effect for preventing the pulsation of the
direct-current bus line voltage Vdc.15
[0063] Note that the configuration in which the
converter of the power conversion apparatus has a boosting
function is not limited to the example in FIG. 10. The
converter 150 of the power conversion apparatus 1 according
to the first embodiment is a passive circuit including20
passive components, and the value of the direct-current bus
line voltage Vdc is determined according to an amplitude
value of the first alternating-current voltage supplied
from the alternating-current power supply 110. However, in
the first embodiment, it is sufficient that the pulsation25
of the direct-current bus line voltage Vdc can be correctly
detected and the pulsation of the frequency component same
as the pulsation can be output from the inverter 310.
Therefore, for example, in the rectifying unit 130, the
rectifying elements 131 to 136, such as diodes, may be30
replaced with semiconductor elements, that is, active
elements, such as switching elements, so as to form the
booster circuit, and the control unit 400 or the like may
31
control an operation of the active element.
[0064] FIG. 11 is a diagram illustrating a configuration
example of a power conversion apparatus 1b according to the
second embodiment. The power conversion apparatus 1b is
obtained by replacing the converter 150 and the control5
unit 400 in the power conversion apparatus 1 according to
the first embodiment illustrated in FIG. 1 with a converter
150b and a control unit 400b. The converter 150b includes
the reactors 120 to 122 and a rectifying unit 130b. The
rectifying unit 130b includes switching elements 161 to 166.10
The switching elements 161 to 166 are, for example,
semiconductor elements and are turned on/off under control
of the control unit 400b. The rectifying unit 130b can
boost and output a voltage by turning on/off the switching
elements 161 to 166. The control unit 400b has the15
function of the control unit 400 and a function for
controlling on/off of the switching elements 161 to 166 of
the rectifying unit 130b. That is, the control unit 400b
controls an operation of the converter 150b. Note that the
rectifying unit 130b may have a configuration in which some20
of the six elements are used as switching elements and
other elements are used as rectifying elements, such as
diodes. In this case, effects similar to those of the
power conversion apparatus 1a illustrated in FIG. 10 can be
obtained. Note that the power conversion apparatus 1b and25
the motor 314 included in the compressor 315 constitute a
motor drive device 2b.
[0065] In this way, the converter 150a in the power
conversion apparatus 1a or the converter 150b in the power
conversion apparatus 1b includes at least one switching30
element.
[0066] Third Embodiment
FIG. 12 is a diagram illustrating a configuration
32
example of a refrigeration cycle application device 900
according to a third embodiment. The refrigeration cycle
application device 900 according to the third embodiment
includes the power conversion apparatus 1 described in the
first embodiment. Note that, although the refrigeration5
cycle application device 900 can include the power
conversion apparatus 1a or the power conversion apparatus
1b described in the second embodiment, here, as an example,
a case will be described where the power conversion
apparatus 1 is included. The refrigeration cycle10
application device 900 according to the third embodiment
can be applied to a product including a refrigerator cycle,
such as an air conditioner, a refrigerator, a freezer, or a
heat pump water heater. Note that, in FIG. 12, a component
having the function similar to that in the first embodiment15
is denoted by the same reference as in the first embodiment.
[0067] In the refrigeration cycle application device 900,
the compressor 315 including the motor 314 in the first
embodiment, a four-way valve 902, an indoor heat exchanger
906, an expansion valve 908, an outdoor heat exchanger 91020
are attached via a refrigerant pipe 912.
[0068] In the compressor 315, a compression mechanism
904 that compresses a refrigerant and the motor 314 that
operates the compression mechanism 904 are provided.
[0069] The refrigeration cycle application device 90025
can perform a heating operation or a cooling operation by a
switching operation of the four-way valve 902. The
compression mechanism 904 is driven by the motor 314 that
is variable-speed controlled.
[0070] At the time of heating operation, as indicated by30
a solid arrow, the refrigerant is pressurized and sent by
the compression mechanism 904, passes through the four-way
valve 902, the indoor heat exchanger 906, the expansion
33
valve 908, the outdoor heat exchanger 910, and the four-way
valve 902, and returns to the compression mechanism 904.
[0071] At the time of cooling operation, as indicated by
a broken arrow, the refrigerant is pressurized and sent by
the compression mechanism 904, passes through the four-way5
valve 902, the outdoor heat exchanger 910, the expansion
valve 908, the indoor heat exchanger 906, and the four-way
valve 902, and returns to the compression mechanism 904.
[0072] At the time of heating operation, the indoor heat
exchanger 906 acts as a condenser and releases heat, and10
the outdoor heat exchanger 910 acts as an evaporator and
absorbs heat. As the time of cooling operation, the
outdoor heat exchanger 910 acts as the condenser and
releases heat, and the indoor heat exchanger 906 acts as
the evaporator and absorbs heat. The expansion valve 90815
decompresses and expands the refrigerant.
[0073] The configurations illustrated in the above
embodiments indicate examples and can be combined with
other known techniques. Furthermore, the embodiments can
be combined with each other, and some configurations can be20
partially omitted or changed without departing from the
scope of the present invention.
Reference Signs List
[0074] 1, 1a, 1b power conversion apparatus; 2, 2a, 2b25
motor drive device; 110 alternating-current power supply;
120 to 122, 141 reactor; 130, 130b rectifying unit; 131
to 136, 143 rectifying element; 140 booster; 142, 161 to
166, 311a to 311f switching element; 150, 150a, 150b
converter; 200 smoothing unit; 210 capacitor; 31030
inverter; 312a to 312f freewheeling diode; 313a, 313b
current detection unit; 314 motor; 315 compressor; 400,
400a, 400b control unit; 401 secondary low-pass filter;
34
402, 404 subtraction unit; 403 filter; 405, 407, 410, 412
pulsation component extraction unit; 406, 408, 411, 413
integration control unit; 409 alternating-current
restoration processing unit; 501, 502 voltage detection
unit; 900 refrigeration cycle application device; 9025
four-way valve; 904 compression mechanism; 906 indoor
heat exchanger; 908 expansion valve; 910 outdoor heat
exchanger; 912 refrigerant pipe.
35
We Claim:
[Claim 1] A power conversion apparatus (1) comprising:
a converter (150) rectifying a first alternating-
current voltage supplied from a three-phase alternating-
current power supply (110);5
a capacitor (210) connected to an output end of the
converter (150), the capacitor (210) smoothing a first
direct-current voltage obtained by rectification by the
converter (150) into a second direct-current voltage
containing a first ripple;10
an inverter (310) connected across the capacitor (210),
the inverter (310) converting the second direct-current
voltage into a second alternating-current voltage, the
second alternating-current voltage being dependent on a
desired frequency; and15
a detection unit (502) detecting a physical quantity
correlated with the second direct-current voltage, wherein
the second alternating-current voltage is controlled
such that a second ripple correlated with the first ripple
is superimposed on an output voltage from the inverter20
(310).
[Claim 2] The power conversion apparatus (1) according to
claim 1, wherein
a frequency of the first ripple is a frequency that is25
twice or six times as large as a fundamental frequency of
the first alternating-current voltage.
[Claim 3] The power conversion apparatus (1) according to
claim 1, wherein30
a frequency of the first ripple is a sum of frequency
components that are twice and six times as large as a
fundamental frequency of the first alternating-current
36
voltage.
[Claim 4] The power conversion apparatus (1) according to
claim 3, wherein
according to an equilibrium state of voltages of5
respective phases of the first alternating-current voltage,
a ratio of the frequency component that is twice as large
as the fundamental frequency of the first alternating-
current voltage and the frequency component that is six
times as large as the fundamental frequency of the first10
alternating-current voltage in the sum is changed.
[Claim 5] The power conversion apparatus (1) according to
any one of claims 1 to 4, wherein
the physical quantity is an instantaneous value of the15
second direct-current voltage containing the first ripple
or an instantaneous value of the current flowing to the
capacitor (210).
[Claim 6] The power conversion apparatus (1) according to20
any one of claims 1 to 5, wherein
the inverter (310) is connected to a motor (314),
the detection unit is assumed as a first detection
unit (502), and
the physical quantity is assumed as a first physical25
quantity,
the power conversion apparatus (1) further comprises:
a second detection unit (313a, 313b) acquiring a
second physical quantity containing a third ripple
correlated with a rotation speed generated by the motor30
(314), and
the second alternating-current voltage is controlled
such that a fourth ripple correlated with the third ripple
37
is superimposed on the output voltage from the inverter
(310).
[Claim 7] The power conversion apparatus (1a; 1b) according
to any one of claims 1 to 6, wherein5
the converter (150a; 150b) includes at least one
switching element.
[Claim 8] The power conversion apparatus (1) according to
any one of claims 1 to 7, wherein10
the fundamental frequency of the first alternating-
current voltage that is a power supply frequency of the
three-phase alternating-current power supply (110) is
periodically calculated.
15
[Claim 9] A motor drive device (2; 2a; 2b) comprising:
the power conversion apparatus (1; 1a; 1b) according
to any one of claims 1 to 8.
[Claim 10] A refrigeration cycle application device (900)20
comprising:
the power conversion apparatus (1; 1a; 1b) according
to any one of claims 1 to 8.